A glass substrate used for liquid crystal display has minute recesses and projections or undulation in its surfaces, which causes a deformed picture image. Accordingly, such minute recesses and projections or undulation should be eliminated with a polishing device. As such polishing device, there has generally been known a polishing device in which a glass substrate held by a carrier is pressed to a polishing cloth disposed on a polishing surface-plate while the polishing surface-plate and the carrier are rotated relative to each other to polish the glass substrate.
Further, in the polishing device disclosed in JP-A-9-141550, a flexible film is disposed at a lower portion of the carrier and pressurized air is supplied between the flexible film and the carrier so that the pressure of the pressurized air urges the substrate attached to the flexible film to the polishing cloth for polishing. According to this polishing device, there is an advantage that the pressurized air in the space between the flexible film and the carrier applies pressure uniformly to each part of the substrate whereby the substrate can be polished flat, and minute recesses and projections in the substrate surface can be eliminated.
However, in the conventional polishing device, there is no proposal about a discharging means for discharging a glass substrate which has been polished and removed from the carrier, from a polishing stage. Particularly, in a case of a large-sized glass substrate, the length of a side of which is, for example, beyond 1,000 mm, the removal and handling of it in the polishing stage and the discharge of it from the polishing stage were very difficult and took a long time to thereby reduce productivity.
With the increase of the size of a liquid crystal display screen in recent years, a polishing device for a large-sized glass substrate, which can solve the above-mentioned problem of discharging a glass substrate after being polished and can improve productivity, has been expected.
The present invention has been made in consideration of the above-mentioned circumstances, and it is an object of the present invention to provide a method and device for polishing a glass substrate suitable for polishing a large-sized glass substrate.